In copending U.S. patent application Ser. No. 897,571, filed Apr. 19, 1978, incorporated herein by reference, a method for the coating of press compartments, i.e., die chambers, on tableting machines is described. The method is characterized in that dissolved or melted lubricants are applied to the inner walls of the press compartments before each pressing operation by means of a nozzle system spraying intermittently and briefly at rapid intervals.
It has been shown in the meantime that with the new high-performance tableting machines, a hydraulically operated intermittent spraying system is still too slow-acting to coat the molding tools before each pressing operation. Moreover, it is fundamentally desirable to keep as small as possible the quantity of lubricant (to achieve an optimal bioavailability, moldability, and a straight-forward and undelayed dissolution of dissolving tablets, e.g., for diagnostic purposes or effervescent tablets). It is therefore necessary that the spraying system be especially capable of applying rapidly in concentrated form the required quantity of lubricant to pressing zones of the molding tools (e.g., the pressing zone in the die cavity) in the shortest possible time, e.g., in a few milliseconds, intermittently, and in a directional manner.